With the recent volatility of diesel fuel prices, increased efficiency takes on a renewed sense of urgency. Advancements in wheel loader designs deserve a close look if you are considering an upgrade.
Manufacturers have made significant advancements in fuel efficiency through a combination of new engine technologies coupled with load-sensing hydraulic systems.
"With the new H Series mid-size wheel loaders (216 to 307 hp), Caterpillar takes a system integration approach to improving fuel economy while improving productivity," says Geoff Perich, product manager for Caterpillar MWL Americas. This includes use of ACERT electronically-controlled engines with multiple-injection fuel delivery, load-sensing hydraulics and a hydraulically driven on-demand (cooling) fan. The result is up to a 5% fuel efficiency gain over the previous models.
This approach carries over to the smaller wheel loaders, as well. Caterpillar's Paul Travaillot estimates the combination of electronically-controlled engines with the load-sensing hydraulics and hydraulic on-demand fan results in a 10% to 15% fuel efficiency advantage vs. a loader without these features. It can even make a difference with novice operators.
"An experienced operator is going to have an advantage," he admits. "But the way our machines are designed, even a novice operator can still realize fuel efficiency."
Volvo also integrates several individual technologies into a complete system. "Two major components of Volvo's wheel loader design combine to create our best in class fuel efficiency — Volvo engines and load-sensing hydraulics," says Volvo's Dan Snedecor. Engines produce high torque at lower rpm than traditional diesel engines. This compliments the load-sensing hydraulics. "Without the load-sensing hydraulic system, our fuel consumption advantage would be minimal. But correctly combining the two yields an extremely fuel efficient design, while still using a conventional-style automatic powershift transmission."
Likewise, Liebherr has developed an integrated systems approach. "All Liebherr wheel loaders feature an advanced hydrostatic driveline system that reduces engine horsepower requirements and increases fuel efficiency," says Tim Doucette, marketing manager, Liebherr Construction Equipment. "The design of the drive system allows the heavy components (engine, hydraulics, etc.) to be placed at the rear of the machine and be utilized as active counterweight. As a result, Liebherr wheel loaders offer less operating weight while maintaining tipping loads."
Case has also optimized the placement of components for maximum efficiency. "On our D Series, we introduced a mid-mount cooling module," says Dave Wolf, marketing manager, Case Construction Equipment. "It moves the engine behind the rear axle, utilizing the weight of the engine as a natural counterweight for more stability. It reduces the weight of the counterweight." In addition, it allows access to the entire engine from the ground.
Engines adapt to the load
The latest round of emissions regulations for off-road engines have actually lowered fuel consumption in most cases. "With the emissions regulations, you start getting into charge air cooling, common rail fuel systems and electronic controls," notes Wolf. These technologies enable the engine to react to the load conditions.
Consider the benefit of charge air cooling. According to Wolf, it results in more cool air entering the combustion chamber. "So you get a cleaner burn and better fuel efficiency," he points out.
Engine electronics have also allowed the engine to adapt to any load changes. "The Caterpillar engine with ACERT technology utilizes electronic control and multiple-injection fuel delivery to ensure outstanding engine performance as engine speeds and load demand change," says Perich. Constant Net Horsepower is a feature that allows ACERT engines to maintain consistent working horsepower while compensating for any parasitic loads.